Amazon’s doomed species to pay ‘extinction debt’

The Guardian, LONDON

The destruction of great swathes of the Brazilian Amazon has turned scores of rare species into the walking dead, doomed to disappear even if deforestation were halted in the region overnight, a new study said.

Forest clearing in Brazil has already claimed casualties, but the animals lost to date in the rainforest region are just one-fifth of those that will slowly die out as the full impact of the loss of habitat takes its toll. In parts of the eastern and southern Amazon, 30 years of concerted deforestation have shrunk viable living and breeding territories enough to condemn 38 species to regional extinction in coming years, including 10 mammal, 20 bird and eight amphibian species, scientists found.

The systematic clearance of trees from the Amazon forces wildlife into ever-smaller patches of ground.

Though few species are killed off directly in forest clearances, many face a slower death sentence as their breeding rates fall and competition for food becomes more intense.

Scientists at Imperial College, London, reached the bleak conclusion after creating a statistical model to calculate the Brazilian Amazon’s “extinction debt,” or the number of species headed for extinction as a result of past deforestation. The model draws on historical deforestation rates and animal populations in 50km by 50km squares of land.

It stops short of naming the species most at risk, but field workers in the region have drawn attention to scores of creatures struggling to cope with habitat destruction and other environmental threats.

White-cheeked spider monkeys, which feed on fruits high in the forest canopy, are endangered largely because of the expansion of farmland and road building. The population of Brazilian bare-faced tamarins has halved in 18 years, or three generations, as cities, agriculture and cattle ranching has pushed into the rainforest. The endangered giant otter, found in the slow-moving rivers and swamps of the Amazon, faces water pollution from agricultural runoff and mining operations in the area.

Writing in the journal Science, Robert Ewers and his co-authors reconstructed extinction rates from 1970 to 2008, and then forecast future extinction debts under four different scenarios, ranging from “business as usual” to a “strong reduction” in forest clearance, which required deforestation to slow down 80 percent by 2020.

“For now, the problem is along the arc of deforestation in the south and east where there is a history of forest loss, but that is going to move in the future. We expect most of the species there to go extinct, and we’ll pick up more extinction debt along the big, paved highways cutting into the heart of the Amazon,” Ewers said from Belem, northern Brazil.

Under the “business as usual” scenario, where about 160km2 of forest are cleared each year, at least 15 mammal, 30 bird and 10 amphibian species were expected to die out locally by 2050. Under the most optimistic scenario, which requires cattle ranchers and soy farmers to comply with Brazilian environmental laws, the extinction debt could be held close to 38 species.

Ewers said the model reveals hotspots in the Brazilian Amazon where conservation efforts should be focused on the most vulnerable wildlife.

The Brazilian Amazon is home to 40 percent of the world’s tropical forest and one of the most biodiverse regions on the planet. About 54 percent of the area is under environmental protection, and over the past five years, stricter controls and better compliance have driven deforestation rates down to a historical low.